docs: def fetch_gist(gist_id, filename=None):
      """Fetch a gist and return the contents as a string."""
      import requests
  
      url = gist_url(gist_id, filename)
      response = requests.get(url)
  
      if response.status_code != 200:
          raise Exception('Got a bad status looking up gist.')
      body = response.text
      if not body:
          raise Exception('Unable to get the gist contents.')
  
      return body